Scsi control zero (scntl0), Register: 0x00 – Avago Technologies LSI53C1000R User Manual
Page 135
SCSI Registers
4-23
Version 2.2
Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
Register: 0x00
SCSI Control Zero (SCNTL0)
Read/Write
ARB[1:0]
Arbitration Mode Bits 1 and 0
[7:6]
A combination of the ARB bits selects either Simple or
Full arbitration.
Simple Arbitration
1.
The LSI53C1000R waits for a bus free condition to
occur.
2.
It asserts SBSY/ and its SCSI ID, contained in the
register, onto the SCSI bus. If
the SSEL/ signal is asserted by another SCSI
device, the LSI53C1000R deasserts SBSY/,
deasserts its ID, and sets the Lost Arbitration bit
(bit 3) in the
register.
3.
After an arbitration delay, the CPU should read the
register to check if a
higher priority SCSI ID is present. If no higher
priority ID bit is set, and the Lost Arbitration bit is not
set, the LSI53C1000R wins arbitration.
4.
When the LSI53C1000R wins arbitration, SSEL/ is
asserted using the
SCSI Output Control Latch (SOCL)
for a bus clear and a bus settle delay (1.2
µ
s). Then,
a low level selection is performed.
7
6
5
4
3
2
1
0
ARB[1:0]
START
WATN
EPC
CRCOK
AAP
TRG
1
1
0
0
0
x
0
0
ARB1
ARB0
Arbitration Mode
0
0
Simple arbitration
0
1
Reserved
1
0
Reserved
1
1
Full arbitration, selection/reselection